Ohio 4R Research Fund Project Stresses Importance of Monitoring Soil Phosphorus Levels

By 4R Nutrient Stewardship|May 12, 2020

As field conditions progress toward being suitable for planting, spring also brings a period of seasonally high precipitation and subsequent flow from tile drainage and surface runoff. In fact, a recent analysis of rainfall patterns from 1975-2017 over the Western Lake Erie Basin (WLEB) showed increasing rainfall amounts and event intensity lead to more water leaving the field per unit of precipitation. As a result, concerns of soil and phosphorus (P) loss in many areas becomes heightened during this time of the year.

The origins of P that may impair water quality varies by physiographic region, watershed, and field. Using 4R Nutrient Stewardship principles of the right source, rate, time, and place reduces losses of recently applied P; however, legacy P losses (P that does not come from recent applications) has been well-documented in soils and sediments. How much P is lost from the legacy pool is a question that many experts are trying to answer.

Recent work from the ARS Soil Drainage Research team (Columbus, OH) has shed some light onto critical relationships between legacy P in soil, tile drainage, and surface runoff. Scientists William Osterholz, Brittany Hanrahan, and Kevin King conducted an edge-of-field study on 39 fields in northwest Ohio from 2011 to 2018. Findings showed a strong relationship between elevated total and dissolved reactive P losses with larger legacy soil test P. The authors pointed to a few other important insights from this study:

  • The size of the legacy soil P pool did not influence behavior of tillage drainage or surface runoff
  • Disrupting the flow path of surface P to macropores and tile lines could mitigate legacy P issues
  • Greater tile flow was associated with greater soil-bound and total P losses, particularly in fine-textured soils.

These insights emphasize the importance of a frequent, comprehensive soil sampling program to accurately assess not only agronomic P needs, but susceptibility to losses as well.

Continue reading at 4R Nutrient Stewardship.

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4R Nutrient Stewardship provides a framework to achieve cropping system goals, such as increased production, increased farmer profitability, enhanced environmental protection and improved sustainability. To achieve those goals, the 4R concept incorporates the Right fertilizer source at the Right rate, at the Right time and in the Right place. See all author stories here.

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